The new year is a good time to look forward and also backward. It is true not just in our profession and personal lives, but also in politics.

President Obama noted as much in a recent press conference, when ABC News' Jonathan Karl asked him what he thought was his biggest mistake in 2013.

Obama avoided specifics, though he did acknowledge that the start of a new year is "always a good time to reflect and see what can you do better next year."

That exchange got me thinking about what I got wrong in the last 12 months. It was an interesting exercise. Columnists, like politicians, hate to admit mistakes. When we miss the mark, we are more likely to finesse our way through an explanation.

What's the point? Our readers can be counted on to note our failings and missteps, whether we acknowledge them or not. Still, if we want to preserve our credibility, it is better to own up to the fact we got something wrong.

Looking back over the past year, I realize that one thing I got wrong - or rather, who I got wrong - was Marco Rubio. I thought the senator from Florida would play a prominent role in immigration reform efforts and lead the debate over how to fix our broken immigration system.

In the spring, it looked as if Rubio was the designated quarterback of the Senate's Gang of Eight. These were the four Democrats and four Republicans who pieced together an immigration reform compromise that was called too lenient by conservatives and too harsh by liberals.

On the weekend before the bill was unveiled in April, Rubio appeared on seven Sunday talk shows, discussing - in English and Spanish - the specifics of the legislation. He seemed to be everywhere, including on just about every list of front-runners for the 2016 Republican presidential nomination. The consensus in much of the media was that this well-spoken and telegenic young man was going places, and that defusing the explosive immigration issue just might be his ticket.

I thought that despite Rubio's wrongheaded support of the Arizona immigration law, which unapologetically promotes ethnic profiling of Latinos, the senator had at least come down on the right side of the discussion over comprehensive immigration reform. I also thought that if he were successful in forging a legislative solution, he might just help bring more Latinos to the Republican Party. That would benefit both Latinos and Republicans by giving the former more options and giving the latter new life. Finally, I thought, this guy was a profile in courage, standing up to right-wingers in his own party. Here was a Cuban-American willing to brave the idiotic hate mail telling him to "Go back to Mexico!"

It didn't turn out this way. Rubio has become a colossal disappointment. His critics, and his own presidential ambition, got the better of him.

He has dropped support for a comprehensive approach - one that enforces the border, gives employers guest workers, and provides legal status to the undocumented - and undermined his own bill. Through a spokesman, he returned in October to advocating something that he supported a year earlier, before all this started: a piecemeal approach that tries to solve at least part of the problem by, for instance, ensuring that agriculture has workers or offering legal status to young people brought here by their parents.

I understand the appeal of half a loaf. Now that Congress has ducked comprehensive immigration reform for another year, the idea of attacking this problem in a piecemeal fashion is looking better and better. But when you're a member of Congress, and you're supposed to lead the way on immigration reform, you should pick a lane and stay there. Otherwise, you're going in circles.

Given his retreat, Rubio may have actually diminished the GOP brand among Latinos. He sent the message that, despite their lip service about immigration reform, Republicans won't stand up to right-wing nativists. He is lost, and so is the party.

Rubio was once front-page news, and now he is yesterday's news. No one cares what he thinks about the immigration issue, because they know that - given time - it'll change.